Electrical heating element



April 21, 1925.

w w WEIR ELECTRICAL HEATING ELEMENT Fil ea Jan. 16'. 1923 Patented Apr. 21, 1925.

UNITED STATES WILLIAM W. WEIR, OF ALAMEDA, CALIFORNIA.

ELECTRICAL HEATING ELEMENT.

Application filed January 10, 1923. Serial No. 611,870.

To all whom it may concern:

Be it known that I, WILLIAM W. WEIR, a citizen of the United States, residing at Alameda, in the county of Alameda, State of California, have invented a new and useful Electrical Heating Element, of which the following is a specification, in such full and clear terms as will enable those skilled in the art to construct and use the same.

This invention relates to an electric heating element and its object is to simplify the construction of such heating elements and to prevent theloss of heat therefrom.

It will be understood by those skilled in the art that heating elements for electric stoves consist of a heat resistant brick of some kind in which a pair of spiral grooves are formed, each of said grooves having a cord of resistance wire therein to deliver heat to the object to be heated. As at present constructed, such bricks have a series of arches over the grooves to aid in holding the coils in place, but with the pres ent invention the grooves have no obstructionover the coils at all, but are undercut to hold them in place.

Another object of the invention attained by the shape of the grooves and manner of holding the coils in place is to make the removal of the coils and insertion of a new coil very much easier than with the present form of bricks.

Another object of the invention is to pro-- vide for holding the coils in place in such a manner as to allow both sides of the coils to heat up evenly, the coils touching the bricks along only two lines.

Another object of the invention is to produce a brick for holding the coils which will have only those perforations'necessary to connect the coil ends with the source of electric current supply, and the grooves are also so shaped as to direct the heat from the coils toward the center of the object to be heated.

Fig. 1 is a plan View of the brick showing a portion of each coil in place.

Fig. 2 is a side elevation of the brick, a portion thereof being shown in section,

Fig. 3 is a sectional view of a portion of the brick on a larger scale to show how the brick holds the coils.

The brick 1 consists of a fiat member having open spiral grooves 2 and 3 formed therein, the grooves beginning near the center of the brick and terminating on opposite sides thereof. The brick also has two notches 4 and 5 for securing it in place in the heating apparatus.

There are also four holes 6 to 9 inclusive through the brick through which the coil ends 10 to 13 inclusive pass to the binding posts 14 to 17 inclusive.

The grooves are undercut as shown at 18 so the coils 19 and 20 drop into place and the spring causes them to press lightly against the overhanging wall.

The overhanging walls extending toward the center of the brick, are so made that the brick touches the coils at only two points in each convolution thereof as shown at 21, 22 Figure 3. The object of this overhang is to direct the heat toward the center of the brick and to hold the coils in place so they will be far enough out of contact with the brick on their undersides as to allow them to heat evenly both on top and bottom as they would not do if in close contact with the brick for 180 or more.

In practice this particular brick is intended to give three heats, but that particu lar arrangement forms no part of the present invention.

It is to be noted that the grooves 2 and 3 have each a continuous smooth surface, without any angles or edges; and that the points of contact between coils 19 and 20 and the grooves arekept few because the bottom of the grooves has a greater curvature than that of the diameter of the coils. In this way a crescent-shaped space is left between the coils 19, 20 and the bottom of grooves 2, 3. I What I claim is as follows,-but various modifications may be made in the construction shown in the drawings and above particularly described form, within the purview of my invention:

1. In an electric heating unit, the combination of an insulating plate having aspiral groove, both walls of which are inclined to the plane of the surface of the groove being formedso that each convolution of the coil contacts with .each wall of the groove at one point only, the two points of contact being spaced apart so that the convolutions do not contact with the bottom of the groove.

2. In an electric heating unit, the combination of a one piece insulating plate having an open groove therein into which the heating element may be inserted, and a helically wound coil of barewire and of uniform diameter throughout its length, disposed in the groove, the convolutions of the coil contacting with the side walls of the groove and being spaced from the bottom of the groove. I

3. In an electric heating unit, the combination of a one piece insulating plate having a groove therein, both walls of the groove being similarly inclined to the plane of the surface of the plate so that one wall of the groove overhangs the groove Without constricting the mouth of the groove whereby the heating element may be readily inserted in the groove, and a helically wound coil of bare wire in the groove, the convolutions of the coil contacting with the side walls only of the groove.

4. In an electric heating unit, the combination of an insulating plate having a spiral groove therein, both walls of the groove being inclined towards the center of the plate whereby radiated heat is directed inwardly toward the center of the plate, and a helically wound coil of bare wire disposed in the groove, the convolutions of the coil contacting with the side walls only of the groove.

5. In an electric heating unit, an insulating plate having an open groove, and a coil of bare wire disposed in said groove, said groove having a continuous, smooth surface with a rounded bottom of reater curvature than the diameter of the C011 disposed therein, and one of the walls overhanging the groove, whereby said coil contacts only with the sides of the groove and at a few isolated points oneach of its turns, and is held'in place by the overhanging wall.

In testimony whereof I have hereunto set my hand this 16th day of December, A. D. 1922.

WILLIAM W. WEIR. 

